Four methods for the calculation of multigroup collision probabilities in cluster geometry are described these are Monte Carlo, full numerical integration, numerical integration over the annuli containing rods combined with the Bonalumi approximation in the moderator annuli, and a ring smearing method again based on the Bonalumi approximation for annular geometry. Results of six group calculations for three tight, natural uranium, D20 lattices are presented in detail. These results suggest that the ring smearing model is suitable for cluster calculations which do not require high accuracy the largest error is in the thermal flux in the outer moderator regions. This error is a general problem inherent in the Bonalumi approximation and is not peculiar to the ring smearing model presented.